Transportation of commodities over ground is effected in a number of ways. Certainly, rail is one viable alternative. It will be understood, however, that trailer trucks are a significant alternative to rail transportation. The movement of items from one location to another location at some significant distance from the initial point is an important goal to be accomplished. Commensurate with the importance of this goal, however, is that the movement be accomplished in a safe manner. Accidents occur on highway systems at an increasingly alarming rate. Certainly, it is important in attempting to minimize accidents that vehicles traveling over roads be provided with adequate braking systems.
The problem is exacerbated in the case of trailer trucks. Because of the significant weights of their cargos, unique problems are introduced. Certainly, it is not sufficient that a cab be slowed down without applying direct braking power to the trailer being towed behind. If no braking power were applied to the trailer, the trailer would be carried, by its momentum, up and over a cab which has been rapidly decelerated by braking action in response to a hazardous situation.
Various types of systems for effecting braking of the trailer component of a tandem arrangement have been developed. One system employs air brakes. In such a system, pressurized air functions to effect movement of a shoe to engage and press against the drum of a brake at a trailer's wheel. Reduction in speed, thereby, occurs.
Another system employs electro-magnetic brakes. In this type of system, movement of a shoe is effected by employment of an electro-magnet which pulls a metal plate. Engagement of a shoe with the drum again creates friction to slow the vehicle.
A number of drawbacks exist with both of these systems, however. Stopping ability will be hampered as a result of excessive heat being generated as a result of friction. Consequently, the ability to slow and stop a vehicle will be reduced.
The present invention is a method and system which ameliorate the problems of the prior art. They employ hydraulic braking which augments the conventional air brake or electro-magnetic brake system of the vehicle.